1. Field of the Invention
The present invention relates to a mobile telephone terminal apparatus having a television telephone function, and, in particular, to an image transmission function.
2. Description of the Related Art
Conventionally, a mobile telephone terminal apparatus having a television function has been known as a mobile telephone terminal apparatus having a function for transmitting image information. The mobile telephone terminal apparatus uses a radio communication line. Therefore, the mobile telephone terminal apparatus has good mobility and can communicate while moving. On the other hand, the quality of the line depends on a state of an electric field. Therefore, the state of the electric field at a place where the mobile telephone terminal apparatus is being used is notified to the user by displaying the receiving electric field level. In addition, when the quality of the communicating line is deteriorated, the communication quality alarm is used to inform the possibility of communication disconnection.
Furthermore, conventionally, a mobile telephone terminal apparatus having a television telephone function has been known as a mobile telephone terminal apparatus having a function for transmitting image information. The mobile telephone terminal apparatus having the television telephone function uses a battery (rechargeable battery) as the power supply. Therefore, the mobile telephone terminal apparatus has good mobility and can communicate while moving. On the other hand, the usable time is limited. Therefore, a remaining amount of the battery is informed to a user of the mobile telephone by displaying the level of the battery remaining amount. In addition, when the battery remaining amount is small, a weak battery alarm informs the possibility of the communication disconnection.
Japanese Unexamined Patent Publication No. 2001-103565 discloses the image transmission when the quality of the line deteriorates during communication by using a mobile telephone terminal apparatus. Briefly, a main control portion monitors a strength of a receiving electric field and/or an error rate of received data. When the deterioration of the communication environment is determined from the monitoring result, the image processor thins down frames of image data imaged by a camera in accordance with an instruction from the main control portion. Thus, an amount of image data to be sent in units through a radio portion is reduced so that the power consumption during the operation can be reduced.
Detection of a receiving electric field level of a mobile telephone terminal apparatus is disclosed in the Japanese Unexamined Patent Publication No. 9-135203. Briefly, both strength of a receiving electric field and error rate (an interference amount between codes) for a control signal in a unit period of time are measured in a mobile radio communication line. Then, the communication quality is displayed in accordance with both of the measurement results. Therefore, the real communication quality can be displayed in the mobile station terminal with better precision.
According to the conventional technologies, an amount of image data to be sent in units is reduced in accordance with the result of monitoring the communication environment. Thus, the power consumption during the operation can be reduced. However, when the quality of the line deteriorates, the code error rate of the sent image data may be increased. Then, the communication with image transmission cannot be continued essentially.
Here, frames of image data are thinned out so as to reduce an amount of image data to be sent in units. Then, the repetition rate of the number of frames is reduced. Thus, screen switching takes a longer time, which is inconvenient for a television telephone.
Furthermore, the quality of the line may deteriorate to a state where a conversation can be continued only with voice. In this case, the image transmission is stopped, and the communication is performed only with voice. Thus, the original function as a television telephone is limited.
This is also applicable to where the remaining amount of a battery is decreased to a state where a conversation can be continued only with voice.